1. Field of the Disclosure
The present disclosure relates to a component for low-temperature applications, a process for producing such a component and the use thereof.
2. Description of Related Art
Transparent glass-ceramics having a low coefficient of thermal expansion are known in the prior art and are described, for example, in DE1902432C, U.S. Pat. No. 4,851,372A and U.S. Pat. No. 5,591,682A. Among glass-ceramics having a particularly low thermal expansion, lithium aluminosilicate (LAS) glass-ceramics are known as “zero expansion materials”.
For example, ZERODUR® is supplied in five thermal expansion classes defined by a certain range of CTE (0° C.; 50° C.):
ZERODUR ® expansion0 ± 100 × ppb/K (0 ± 0.100 × 10−6/K)class 2ZERODUR ® expansion0 ± 50 × ppb/K(0 ± 0.050 × 10−6/K)class 1ZERODUR ® expansion0 ± 20 × ppb/K(0 ± 0.020 × 10−6/K)class 0ZERODUR ® expansion0 ± 10 × ppb/K(0 ± 0.010 × 10−6/K)class 0 SPECIALZERODUR ® expansion 0 ± 7 × ppb/K(0 ± 0.007 × 10−6/K)class 0 EXTREME
Glass-ceramics are classified according to the average or mean coefficient of thermal expansion (CTE) (T0; T), determined usually in the temperature range of from 0 to 50° C. However, a low value for CTE in the range of about room temperature (0° C.; 50° C.) is not necessarily associated with a low value for CTE at very low temperatures. Owing to the poorer expansion class at application temperatures close to absolute zero (−273.15° C.=0 Kelvin), ZERODUR® is therefore replaced in some applications by silicon carbide SiC whose CTE in this region is smaller than that of ZERODUR®.
Apart from the absolute value for the CTE of a material, the compatibility of the CTE, i.e. similar thermal expansion curves, with composites which are likewise used, for example carbon-fibre-reinforced plastics (CFRP) also plays a role for the application. Here, SiC has the disadvantage that although it has a thermal expansion curve similar to that of CFRP close to absolute zero, the thermal expansion curve of SiC at higher temperatures (>−120° C.) deviates significantly from the thermal expansion curve of CFRP. Thus, stresses occur in composite components composed of SiC and CFRP when the composite components are cooled, and these stresses can significantly reduce the durability of the composite components.
It was therefore an object of the present disclosure to solve the abovementioned problems. In particular, an improved zero expansion glass-ceramic for low-temperature applications should be provided. The CTE of such a component should be optimized in respect of the application temperature. Furthermore, a zero expansion glass-ceramic whose thermal expansion curve is compatible with (similar to) the thermal expansion curve of CFRP should be provided.